Currently enzymes have attracted the attention of the world due to their wide range of industrial applications in many fields including organic synthesis, clinical analysis, pharmaceuticals, detergents, food production and fermentation. Enzymes are gradually replacing the use of harsh chemicals in various industrial processes (Malathu et al., 2008). Proteases represent one of the three largest groups of industrial enzymes and account for about 60% of the total worldwide sale of enzymes. Enzymes are established active ingredients of detergents and cleaning agents. Proteases induce degradation of protein-based soiling on the items to be cleaned, such as textiles or hard surfaces. Various gram-positive microorganisms are known to secrete extracellular and/or intracellular protease at some stage in their life cycles. Many proteases are produced in large quantities for industrial purposes. A negative aspect of the presence of proteases in gram-positive organisms is their contribution to the overall degradation of secreted heterologous or foreign proteins.
The classification of proteases found in microorganisms is based on their catalytic mechanism which results in four groups: the serine proteases; metalloproteases; cysteine proteases; and aspartic proteases.
Proteases are degradative enzymes which catalyze the hydrolysis of peptides. They are obligatory components for microorganisms which are involved in the utilization of proteinous nutrient, releasing of protein, zymogen activation, autolysis, spore germination and other physiological phenomena (Cappuccino and Sherman, 1992). Proteases represent the class of enzymes which occupy a pivotal position with respect to their physiological roles as well as their commercial applications. They perform both degradative and synthetic functions (Rao et al., 1998). Proteases are one of the most important groups of industrial enzymes and account for nearly 60% of the total enzyme sale (Brown and Yada, 1991; Escobar and Barnett 1993; Adinarayana et al., 2003).
Thermostable enzymes can be obtained from mesophilic and thermophilic organisms; even psycrophiles have some thermostable enzymes. Thermophiles represent an obvious source of thermostable enzymes, being reasonable to assume that such character will confer their proteins a high thermal stability. The industrial use of proteases in detergents or for leather processing requires that the enzyme be stable at higher temperatures. Thermostable proteases are advantageous in some applications because higher processing temperatures can be employed, resulting in faster reaction rates, increase in the solubility of nongaseous reactants and products, and reduced incidence of microbial contamination by mesophilic organisms.
Accordingly, the present invention relates to a thermostable protease useful as an enzyme for industrial use, a gene encoding the same and a method of producing the enzyme by genetic engineering technique.